First, shade some cells based on the nonogram clues. Some cells are already shaded to help you. Then, make a loop (possibly crossing itself) through all the shaded cells (and only the shaded cells) such that adjacent cells in the loop are always a knight's move apart. The numbers in the corners of some cells give you their positions in the loop (from 1 to 28). The letters on cells are only for getting the final answer. This puzzle is at this penpa link. Answer checking requires both the nonogram and knight-move loop (you can make knight-move loops with "Line" mode's "Free" setting).